Welsh 
Water Cycle in a Bag
You will need:
- Some water.
- A clear plastic 'zip lock' type bag
What to do:
- Put a small amount of water in the bag, and then blow into the bag and try and trap some of the air in the bag whilst sealing it.
- Place the bag on a sunny window sill, or over a radiator. Some of the water will evaporate, rise, and condense on the sides of the bag. This is a simplified, miniature version of what happens in the atmosphere.
Possible Extension
Why not draw a simplified picture of the water cycle on the outside of the bag? It should show the sea/ lakes/ rivers, evaporation, condensation, clouds and precipitation.